Memory management is one of the most fundamental issues of modern computer systems. Typically, a computer system will include a hierarchy of memory that ranges from a small, fast cache of main memory that is placed in front of a larger, but slower, auxiliary memory. The cache is generally implemented using a physical memory, such as RAM, while the auxiliary memory is implemented using a storage device, such as a disk drive or hard disk. Both memories are usually managed in uniformly sized units known as pages.
In order to improve performance, many computers and operating systems today implement virtual memory for the applications running on the computer. Virtual memory is where the computer system emulates that it has more memory than the computer system actually physically possesses. For example, most computer systems utilize 32-bit processors. Hence, a computer system is theoretically capable of providing a virtual memory of approximately 232 bits or approximately 4 Gigabytes, even though the physical memory is usually much smaller.
In order to provide a virtual memory of this size, the computer system runs the application or process in a memory address space that is virtual, i.e., not tied to the physical memory. The computer system will then swap pages in and out of a cache in its physical memory in order to emulate the virtual memory. During operation, an application or process will continually requests pages using virtual memory addresses. In response, the computer system will translate the virtual memory address into a physical memory address and determine if the page is present in the cache (i.e., the page is resident). When a requested page is not present in the cache, it is called a cache “miss” (or page fault), and the requested page must be retrieved from storage. However, when the cache is full, before a new page can be brought into the cache, another page (known as the victim page) must be evicted to storage.
Many applications running on a computer system utilizes confidential or sensitive data, such as encryption keys, passwords, account numbers, and the like. Unfortunately, as noted above, an application is provided a virtual memory and portions of that virtual memory are actually swapped in/out of storage, which is generally unprotected from tampering. Any data read by a process that was originally encrypted can be found as plain text in swap storage, if the process used data that was swapped out to storage. Moreover, it is possible for passwords and the confidential data to reside in storage for long periods of time, even after rebooting the system. This is contrary to what most users expect, i.e., that all confidential data vanishes with process termination. If the integrity of the system is compromised, an untrusted party may gain access to the confidential data that has been swapped out and retained in storage.
Accordingly, it would be desirable to provide methods and systems for designating and handling confidential data.